.....There is no such thing as a Waterproof phone, only water resistant. Always has been that way. No manufacturer can guarantee water resistance, the phone will receive a water resistance rating only and your mileage may vary. Your best bet in the future is to buy a case with additional water resistance to hep protect your next phone.
Sadly you have an expensive paperweight. I don't see any recourse for you at this point short of paying someone to fix the phone or buying a new phone. The manufacturer won't be of much help unless you can prove it was due to a known defect.
When I purchased my Doogee S60 at GearBest I was very happy with it. Beautiful, fast working, reliable, incredibly solid body, only positive points for almost a year of use.
...Until the miserable misfortune of having it wet! Then everything turned into crap!!
My phone immediately stopped working as it got wet because the top and bottom rubber lids DIDN'T PREVENT WATER TO GET INSIDE THE EQUIPMENT!!
I have contacted GearBest but I was simply accused of equipment misuse and left talking to myself... Now I have a beautiful €200 brick.
I'm totally clueless about what should I do... Any advice on how to push further my complaints or on how to recover(?) my phone?
Thanks a lot!

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic